Why is the problem of obesity so damned tricky?

1. Why is the problem of obesity so damned tricky?

 

A lot of us are fat. Fatness increased dramatically in the 20th century, especially since the 1980's in the US.  We don't like being fat in general.  When it becomes extreme, body fat usually doesn't look good to us and can lead to health problems, diminished longevity, and restricted quality of life.  Some distributions of body fat are worse than others for health or for appearance, but at some point it eventually looks bad to us and detracts from our lives.  

 

1. Just Theories are Well Communicated and Popular but Wrong

 

If we find fat so problematic, why haven't we simply found good solutions for it and begun to apply them?  Most people can lose some body fat temporarily by some combination of depriving themselves of some particular kinds of preferred foods, trying to force themselves to eat less,  and trying to force themselves to be more active.  Most people end up going back to their original body fat levels, or greater, after a few weeks, months, or years of that effort.    There is no lack of simplistic just theories about why this is happening:

 

Fat people are just lazy and not exercising enough self-control over their eating and exercise

Fat people are just gluttons who eat too much

Fat people are just eating too much carbohydrate

Fat people are just eating too much starch

Fat people are just eating too much sugar

Fat people are just eating too much fat

Fat people are just maintaining their weight at a genetic set point

 

Although each of those ideas is wrong in its own particular way, and they are each perhaps partly right in some sense,  it is the just part that is most wrong of all.  The just theory is a special kind of problem in itself that is part of the reason fatness is so difficult to address.

 

Here's my central claim: scientific consensus is not just a matter of certain opinions winning out over others, the problem of obesity is understood in broad form as a scientific consensus even though many the details are complex and some of our knowledge of the factors is undoubtedly incomplete.  There is a rough scientific consensus about various aspects of obesity across fields of physiology, nutrition, psychology, neuroscience, and medicine.  It is not just the confusing mess that appears in popular media.

 

I also claim: this consensus understanding is not what is published in most diet, fitness, and weight control books.  In fact, a sizable number of popular books on diet and weight control conflict dramatically with the scientific consensus, but are marketed as if they were new and revolutionary new findings.    This has contributed heavily to the confusion and so added to the problem. 

 

 

B. The Scientific Consensus is Poorly Communicated

 

In the stories that journalists tell to try to communicate their own interpretations of the obesity and health research, they have often engaged the science compellingly but not faithfully.  We now know some very useful things that are not well communicated, or are even ignored or denied by popular authors with their own agendas, or get lost in the media confusion:

 

1. The theory that people can control their weight by exercising self-control at each eating or activity decision is simply wrong.  

 

No one has that much self-control against an environment that constantly tempts them.  The psychological study of self-control reveals that variation in impulsiveness is indeed a factor in all sorts of problems, including obesity, and that people can often learn skills to compensate for impulsiveness, but these do not rely on individual acts of self-control.  Self-control is always finite, and we successfully compensate for impulsiveness by not just exercising self-control in each decision, but also even more importantly by altering our environment and altering our habits so that we reduce the need to exercise our always finite capacity for self-control.

 

2. All of the theories of specific  macronutrients causing  us to become fat are simply wrong.

 

The theories of metabolic advantages of particular diets (low carb, low fat, vegan, paleo, etc.) have all been falsified scientifically so far.  Obesity is in general at the population level not caused by everyone's metabolism being "broken" by certain foods nor is it "fixed" by eating certain foods. 

 

We know for a fact for example that low carb diets do not cause people to lose weight by any special "fat burning mode" as is often claimed in popular diet books.   We know that simply eating a lot of fat or a lot of sugar while keeping energy intake constant does not cause us to gain more body fat.  We know for a fact that the theory of obesity being caused by insulin levels rising due to eating  too much starch or sugar is simply wrong.  People become fat when they take in too much energy regardless of the source and they lose body fat when they take in less energy regardless of the sources they eat less of. 

 

That doesn't mean people respond equally to every kind of diet.  It's just that the reasons are not metabolic.  The reasons have to do with reward, satiety, and sometimes individual differences.  But the metabolic differences between different macronutrient strategies is based on thinking that has already been tested and falsified.  

 

Also  this wouldn't have to be true necessarily.  It isn't a logical necessity that foods have no powerful differential effect on absorption and conversion to fat and fat storage.  It's not just a matter of thermodynamics or conversation of mass and energy.  It is possible that our biology might have allowed us to take in some kids of nutrient, extract energy or chemicals from it, and excrete most of it without gaining body fat.  But it turns out to be false.  The reason is not conservation of mass and energy, the reason that our biology is particularly efficient in using nutrients and in storing the surplus energy. 

 

We might truly have discovered some  differential metabolic effects that prevent us from processing certain foods into fat (and that is exactly what many popular authors have claimed) but … it turns out that it doesn't seem to be true in general, and certainly not as a reliable  way to lose body fat permanently.  The small differential effects of nutrients on metabolism are sometimes used to good effect in short term efforts at bodybuilding and fitness, but they are not a reliable approach to obesity in general.

 

3. Consequently, No macronutrient restriction strategy is a best practice diet for everyone. 

 

Framing the problem of fatness as if we  need to choose between popular branded diets is more often part of the problem than part of the solution.  Branded diets are generally based on a particular just theory.  

 

Debates over low carb, low fat, low sugar, low starch, low glycemic, high fiber, vegan, paleo, and so on are mostly based on asking the wrong question: "what specific food is making me fat?" 

 

Cutting out problematic "trigger" foods can be helpful for particular people, but not for metabolic reasons.  Also cutting out entire classes of food can help at least temporarily lose weight.  This is also not for metabolic reasons.  This is because we tend to reduce intake more than we compensate, at least for a while, when we cut out entire classes of food. 

 

Some of those strategies work better than others in the short run.  But it turns out with those macronutrient restriction strategies that it really doesn't matter which class we chose to cut out in the long run. 

 

People who successfully reduce intake by restricting carbohydrates and people who successfully reduce intake by eating vegan or by eating "paleo" are all losing weight because they are taking in less energy, not because of metabolic advantages. 

 

So long as we can sustain the calorie deficit with that strategy, we lose body fat.  That's wonderful for the people who end up with a strategy they can sustain, and we can find some success stories for many different strategies.  Strategies that restrict entire classes of nutrients end up being unsustainable for most people  in the long run though and the claims often made about any of these having unique metabolic advantages for weight control have been soundly falsified.  

 

4. People do not regulate their weight to a particular inherited set point.

 

This is the opposite problem from the panacea solutions.  This one reinforces our tendency to give up.  Fatness and leanness often run in families, but not because our genes have a built in weight that we are fated to maintain.  It is because of all of the various factors that go into activity, reward, impulse control, individual metabolism, and habit formation, how those interact with specific environments, and because we often inherit things in addition to our genes.  Animals in their native ecological niche tend to regulate their weight very tightly and people who try to lose weight often end up back at the same weight.  But these are as much a result of stable aspects of their environments as stability in their weight regulation.  When we re-engineer out environments we end up altering weight regulation.  The efficiency of our biology and the stability of our dispositions are powerful factors in making obesity a difficult problem but they do not  make it impossible to solve. 

 

I'm going to try to do more than just add my own personal just theory to the already confusing and conflicting list.  What I'm going to try to do is navigate the available evidence to show what is going on and make sense of why the problem is so difficult and what people are doing when they do manage to succeed.

 

3. The Backlash Culture Against Obesity Does More Harm Than Good

 

So the "obesity epidemic," as it has often been called, has led to a culture of backlash against fatness.  By that I mean a commonly shared negative attitude toward fatness and toward fat people.  We have mobilized mightily against the problem in all sorts of ways.  Some of those have unfortunately probably made the problem worse. 

 

The backlash against fatness might have been a good thing if it had led to a problem solving culture that recognized the biological, psychological, cultural, and economic dimensions problem realistically, helped us understand it, and began providing realistic solutions.  Obesity researchers have sometimes attempted to offer realistic solutions, especially focusing on preventing obesity in children where we can potentially have the most effect.   

 

But realistic problem solving is definitely not most of what has happened so far.   What we have instead is:

 

1. The problem remains: most people who try to lose body fat end up going from diet to diet or from one exercise program to another , succeed for a while, and then give up.  Eventually many give up on the problem entirely as hopeless.  In effect, we often give up on ourselves.  This is especially true when we buy in to the popular misconception that obesity reflects a simple failure of willpower.  Fat people are often stigmatized as lazy and they feel like failures, which generally makes the problem worse rather than better.

 

2. The food industry exploits the situation by creating and marketing niche "diet" and "health" products that supposedly address the problem but which rely on outdated theories, popular misconceptions, and strategically selective interpretations of research.  The market for high density rewarding "diet" foods for example was created to exploit medical advice to eat less food by eating less fat.  The advice was oversimplified and the new market for diet foods probably added to the problem significantly by exploiting it.  Their goal is selling more food product rather than improving health, which most often turn out to be conflicting priorities.     They become part of the problem by flooding us with false solutions and misleading information. 

 

3. The fitness industry exploits the situation by creating complex dietary and exercise programs that are oriented to short term bodybuilding or fitness goals and then marketing those as solutions to obesity. 

 

4. Popular authors tout their range of idiosyncratic interpretations and solutions, each trying to make sense of the confusion but they mostly end up increasing it.  Popular diet just theories by journalists and doctors very often end up inadvertently creating even more confusion.  

 

So the backlash culture in these various dimensions,  far from helping to lessen the problem, has exacerbated and perpetuated it in several specific ways:

 

• It increases the difficulty of the problem for individuals psychologically, by fostering confusion and then discouragement and self-loathing.  By emphasizing willpower in unrealistic ways, and relying on solutions that require extraordinary short term efforts, we make people less able to succeed rather than more able to succeed in the long run.

 

• It adds to choice confusion when we try to make decisions and are led astray by the marketing of product rather than decisions in our own best interests.  Unless things like "diet foods" and "bootcamps" and "extreme weight loss" are themselves actually viable solutions to obesity (which they are not in general) they become new sources of both confusion and discouragement.

 

• It reinforces the epistemological problem of cynicism.  Thinking we are all scientific experts  who are well situated to simply choose between the popular diets and popular theories that seem most plausible to us prevents us from learning from the actual research and prevents us from moving toward more realistic solutions.  We become easy prey for every scheme that comes along. 

D. Science Cynicism and Overly Broad Mistrust of Expertise

 

Journalists writing about the problem of obesity have responded to this ongoing confusion by either claiming we don't know what causes obesity or by trying to promote a particular new finding.  The problem is very complex in some ways, but it is very misleading to say that we don't know enough about it to move toward better solutions.  The journalists who say we don't know the answer are a minor concern though, they are at least sincerely trying to be good communicators of the science and clear up the confusion.  The ones who are really dangerous are the grandiose prophets of false information. 

 

What we usually have is a theory that catches the interest of the journalist and then they confirm it by gathering information and telling stories that reinforce their own theory.  This is a compelling and powerful way to communicate, but it offers no assurance that they are getting the science right.  And while we sometimes find out about truly revolutionary ideas this way, as it turns out, these "sciencey" storytellers are most often getting as much of the science wrong as they are getting right.   

 

These "sciencey" journalists often end up asking bad questions and then we end up talking about the wrong things.  I think this is a big part of the problem and the reason I have written this book.  I hope to describe what we know about the problem of fatness without falling into the common trap of arrogance and confirmatory bias, but of course I can only argue my own perspective.  I could be wrong about the scientific consensus, but I will do my best to communicate it as faithfully as I can. 

 

The unconstrained confirmatory bias by journalists wouldn't be so bad by itself in some cases, since they do sometimes bring information to light that was not previously well known.  At least some people would benefit from some of this information.    But these folks often then read some scientific literature to try to bolster their articles and books and I feel they often do a hatchet job on it.  They can't reconcile their idiosyncratic theories with the existing evidence so they start claiming that the evidence that conflicts with their own theory was due to "corrupt researchers."  This ad hominem strategy has been a highly successful one for some authors, but it is an unfair way to argue and much worse, it plays into general cultural cynicism of science.  That part is extremely bad for the rest us.  It means we perceive the science as arbitrary or a matter of choosing sides based on what sounds plausible or what seems to work for some people.  It feeds the popular trend for imagining that everyone is naturally capable of evaluating scientific evidence by virtue of "common sense." 

 

What often happens, I believe, is that we end up mistrusting expertise, which is in itself a very serious problem.   That fact that we find so many false or misleading claims of expertise makes the problem of finding, trusting, and interpreting legitimate expertise even more of a challenge.    Nutrition and health sometimes involve on complex technical knowledge and interpreting rich patterns of seemingly conflicting evidence.  This kind of interpretative skill and knowledge is not something we possess as part of our "common sense."  It is something that requires not only understanding "critical thinking" in general, but also requires domain-specific knowledge in the specific fields in question. 

 

The backlash culture and especially cynicism of real expertise has fed bias and arrogance by various popular journalists who then set the tone for popular conversations in unproductive ways.  Although they may have a lot of charts and graphs and selectively cite and interpret a lot of research, rarely do journalists engage the research deeply and competently and systematically and put it into context.  Rarely do they make a distinction between different kinds of evidence and different quality of evidence in order to do a skilled job or drawing general conclusions from the existing science. 

 

The biggest problem with many of these popular authors is their grandiosity.  They think they've discovered a pattern that everyone else has missed or they have some limited success with some people and they proclaim to the world that they have the solution.  Grandiosity exploits uncertainty and cynicism to produce cults of misinformation that are self-perpetuating and extremely difficult to address with reasoning and evidence.  

 

 

Summary of Why the Big Fat Problem is So Tricky

 

Summary of broad factors making the Big Fat Problem so nasty:

 

Problem Factor	Class of Factor	Associated Bad Thinking
We tend to think in terms of simple actionable heuristics we can act upon when we make decisions.  What food is causing me to get fat, so I can stop eating it and lose weight?  What foods should I eat to lose weight instead?  Our need for actionable heuristics makes us especially vulnerable to just theories, and just theories of complex outcomes are typically wrong.	Oversimplification	"Obesity is just a matter of eating more of … or eating less of  …"
The science is often distorted into oversimplified advice.  The scientific consensus relies on expertise to understand and is hard to communicate in terms of actionable steps so it gets lost in the confusion of just theories.   We end up systematically asking the wrong questions and arguing without regard to the existing patterns of evidence.	Oversimplification	"One study constantly contradicts the previous one, so it's all really useless information, we should just pick the authors we agree with and follow their advice"
Our collective cultural assault on fatness has led to a backlash culture that makes things worse and leads to additional problems.	Unintended Consequences	"Being fat is really bad, stop being so lazy!  Just do this… "
Journalistic arrogance and widespread science cynicism exploit the problem of ubiquitous expertise	Knowledge Cynicism	"We're all scientific experts, including me!  Forget the scientific consensus, this sounds like a good way, follow me!"
"Sciencey" storytelling journalism	Poor science communication	"Telling stories about research and researchers is a great way to learn the science!  The details of weighing evidence are boring and irrelevant and people aren't able to handle it."
Industry interests driven by economic and business concerns that often end up conflicting with public health or individual interests of consumers	Economically Driven Consumer Culture	"People citing research in their ads and branding their products for health are generally offering valuable new choices for us."

Can Blender Food Help Us Lose Body Fat?

I use the blender for weight control as do a lot of people, but I've been very careful about tracking my results and I've found that I've had  varying success using the blender as a weight control tool.    I think I've discovered some of the reasons for the variance.   I'm not interested in motivational stories or anecdotes or testimonials  or selling recipes or blenders here, I'm interested in the specifics of what makes the blender a useful tool for weight control and what makes it less useful in some cases.   

The main ingredients in a smoothie intended for weight control are fruits and vegetables.  Protein powders often figure in recipes but I want to consider them separately because in most cases they are not used for weight control specifically.  There are exceptions to that such as protein-sparing fasts, but it is the fruits and vegetables that most advocates of blender foods are talking about for the most part. 

In general we think of fruits and vegetables as healthy.  Not much to argue with there, but I want to first examine the basis of this idea so we have a clear understanding of what we are talking about because in this case the details matter and not just the general principle that fruits and vegetables are mostly very healthy food.   

In general we tend to accept the assumption that fruits and vegetables are healthy compared to most of what most people eat.  The most convenient and least expensive foods and ones we value most tend to be the least healthy in general.  Compared to those, fruits and vegetables are clearly more conducive to good health.  

There are two important points of contention though:

1. "Smoothies" often contain ingredients for flavor that are not just blended fruits and vegetables and maybe some protein powder.  They can contain a lot of added sugar, and significant added fats because  those often make the drink a lot more appealing.  However that is a concern mainly if you buy commercial drinks or  if you are careless about the recipes you use.

2. There is also evidence that drinking food can sometimes have completely different effects on satiety than eating it.  This is a much more important concern to me and one that I want to examine in more detail.  The tricky part is that the effects of drinking calories can be good or bad depending on other things. 

For the moment let's assume we are intelligently blending fruits and vegetables, and that the resulting drink is healthier in most ways than commercial soft drinks.   That assumption is probably not too much of a stretch.  The question I'd like to address is specifically whether we can generalize that adding daily smoothies to our diet can improve our ability to regulate our weight, whether it can be a detriment, or whether it tends to be a neutral or indeterminate factor.       

First, let's get a scientific handle on fatness.  The problem of obesity at a population level has a lot of complicated aspects and the biology of metabolism is also very complex, but advocates of various products and services have often used that complexity to distract us from what are fairly simple overall facts of the matter.  So let's start by taking a very simple high level cut at the problem of human fatness from a biological perspective.

Kelly Brownell, an expert in nutrition and weight disorders, describes the overall situation as clearly as any problem description can be stated:

"The simple story is that biology seeks out an energy-dense diet, the environment provides it, and we have runaway obesity." [1] (p. 35)

This is sometimes known as the "mismatch" framework because it reflects our observation that our environment has become less well matched over time with our biology in some ways.  We have made great strides in exploiting the widespread animal evolutionary selection for efficiency in the form of preferring an energy dense diet when it is available.  We seek out sugar, fat, variety, and the flavors we associate with fats and carbohydrates especially.  Our cultural environment exploits this in selling food.    That's the simple truth of why so many of us are fat.  Our stable biology preferring energy dense foods  provides a vulnerability that our environment has come to exploit. 

Obesity, or runaway excess fat tissue, is relatively uncommon outside of humans, the companion animals of humans, and the animals domesticated by humans.  In general when animals have equally palatable or equally unpalatable choices of different macronutrients, they tend to balance them pretty well rather than becoming malnourished or overnourished.    Under conditions of their natural environment, animal preferences in food tend to serve them well most of the time, just as we would expect.  Weight is regulated in a very stable way under those conditions.     Animals evolved to eat in a way that helps them survive in their natural habitat, by taking advantage of the food sources available to them.  

The bad news is that something relatively uncommon in nature is now very common in human environments:  abundance in the form of an amount and variety of energy dense foods that was very rare in earlier times.  The seemingly good intake regulation animals do in natural environments, where scarcity is the rule, is easily overridden by simply making greater amounts and greater variety of foods available of the sort we tend to prefer. 

We are not wired to regulate our weight, we are wired to thrive in natural environments by strongly preferring energy dense foods in order to take advantage of them when we find them, and there is apparently no natural mechanism that effectively compensates for that preference by eating less of them under those conditions. 

In experiments with rats, the preference is so strong that they eat themselves into protein deprivation when either more fats or more carbohydrates or both are provided than proteins.  [2]  Rats may seem pretty far removed from us in some ways, but the pattern is suspiciously familiar in human environments as well.  Greater availability of higher energy density foods leads to eating more of those and neglecting other sources of nutrition, to the detriment of our health.

So we don't need to look at a lot of complicated issues in nutrition to see why fruits and vegetables are offered as favored foods for weight control.  However I think we do need to be suspicious of whether simply adding more of  those to our diet will have the desired effect of competing successfully with the higher energy density foods that make us fat.  Will drinking more green smoothies lead to eating less loaded fries and mega burgers and drinking less gargantuan soft drinks?  That's the promise of the blender as a weight control tool, at least in the ads for smoothies and blenders and smoothie recipes. 

We have clear-cut evidence that fruits and vegetables are in general less energy dense and yet are still satisfying sources of nutrition compared to most of the food that comprises the average American diet.  The strategy of reducing energy density in general has been supported by research and argued by leading experts in weight regulation such as Barbara Rolls :

"A growing body of laboratory-based, clinical, and epidemiological data suggests that low-energy-dense diets are associated with better diet quality, lower energy intakes, and body weight. Dietary energy density can be lowered by adding water-rich fruits, vegetables, cooked grains, and soups to the diet, and by reducing the diet’s fat content." [3] p. S98 

So the argument for replacing at least some portion of our energy dense foods filled with added sugars and fats with satisfying but far less energy dense foods like fruits and vegetables appears to be very defensible, so long as we are also somehow still getting the nutrients we need that might not be easily found in fruits and vegetables.  The advocates of smoothies rarely suggest that they should entirely replace other foods with smoothies, so that doesn't seem like a big concern to me so long as people are not relying entirely on smoothies for their nutrition.

Replacing some of our energy dense convenience foods with less energy dense fruits and vegetables certainly seems reasonable.  So we might well agree in principle that adding fruits and vegetables to our diet can help regulate our weight.  But does it actually work that way if we simply add fruits and vegetables to diet otherwise filled with convenience foods?   Do we actually start eating less of other things if we somehow get ourselves to eat more fruits and vegetables?  Or do we end up just adding more "healthy" calories on top of what we already eat?

The question is not just the trivial one of whether forcing ourselves to eat tons of veggies temporarily prevents us from eating a cheeseburger, or whether that would be a good strategy.  The question is whether adding fruits and vegetables in some enjoyable way actually  helps us eat less of other things in the long run in a way that causes us to take in less total energy.   That would be a legitimate aid to weight control. 

Or are green smoothies a minor convenience that still relies on brute force self-control to replace the more attractive foods we crave? 

And if eating more fruits and veggies does help, does it still help if the fruits and vegetables are eaten as a liquid?  There is a real possibility that it might make a difference.    These are the real questions I want to explore.

Phrased this way, many of the vast complexities of nutrition and metabolism are mostly irrelevant.  What I want to know is whether smoothies can actually help with weight control, which means the ultimate deciding factor is whether adding them to our diet causes us to take in less energy overall, without taking other measures.  That's a strongly stated but relatively common version of the claim made for why smoothies are supposed to be useful for weight control.

Fruits and vegetables are low in energy density mostly because of their high water content and their low fat content.  Their fiber content contributes as well, but to a lesser and more variable extent.  The low energy density due to high water content and low fat content also seems to be the primary reason why fruits and vegetables are relatively high in satiety (we  tend to compensate for eating them by eating less later) as well as satiation (we tend to find smaller amounts satisfying  and stop eating sooner).   [4] p. 6

If fruits and vegetables are generally useful in regulating our weight, the best argument I can find is that they replace higher density nutrition with lower energy density nutrition without motivating us to eat more to compensate.  If we ended up more hungry a few hours later as a result of taking in less energy dense foods now, we would still be relying on our willpower to lose weight and the fruits and vegetables would not actually be helping us lose weight in the strongly stated sense. 

So do fruits and vegetables have this effect of helping us take in less energy while not compensating later? 

And do they still have this effect if prepared in a blender first?

In the latter 20th century, the rate of obesity rose dramatically and unexpectedly along with the amount of money we spent marketing and buying convenient foods that are very high in added sugars, added fats, enhanced flavors, portion sizes, and energy.   It is very unlikely that this was a coincidence.  We started eating more because  foods that exploited our preferences became more readily available and appealed particularly to our decision making by appealing to our taste preferences and our preference for economic value.  Nor did we compensate for the increased intake by moving more.  If anything technology changes have led us to move less and exert less physical effort in our daily lives.  As a result the environment came to overwhelm our ability to regulate our own weight. 

Popular theories that preferentially blame fats or carbohydrates for obesity are mostly missing the point.  We became fat when we started eating more of everything, and we did that because of increased availability of high energy foods that suit our natural preferences, not simply because fats or carbohydrates are fattening.      

The crux of the problem of fatness is increased intake, not whether we eat "healthy" foods.  That's why the question of whether fruits and vegetables help us eat less is crucially important.  We eat more now across all of the major food groups, not just the "unhealthy" foods, so we can't lay the blame for obesity entirely on those.  The increased intake that led to increased obesity included fruits and vegetables, not just French Fries  and soft drinks.   Adding fruits and vegetables to our diet in general as a population has not by itself magically pushed out junk food or reduced our overall calorie intake, and there is little population evidence to suggest that it should.   The evidence that simply adding fruits and vegetables to our diet would compensate for overeating is not terribly compelling at a population level.    But what about experimental evidence? 

Considering how commonly it is recommended, there is surprisingly little direct evidence regarding the effect on weight control of adding fruits and vegetables to our diet.  Most research where higher energy density foods were replaced with fruits and vegetables was relatively short term and also included explicit instructions and assistance in avoiding compensating for the added calories.  So we don't really know whether (or how much) adding fruits and vegetables really helps us eat less or helps us eat less in a later meal.  We strongly suspect it is at least a factor though because low energy density foods do tend to result in both higher satiety and higher satiation.   The fiber content of those foods may also play a secondary role. 

For the most part when we are not relying on external cues for how much to eat and we make use of internal sensation, it is the  weight and volume of what we eat that makes the difference in how much we eat rather than the amount of energy it contains or the glycemic loading, so long as it has the right sensory properties that we experience it as substantial food. [5]   Surprisingly, since so much diet advice mentions glycemic index, it does not appear that carbohydrate content or glycemic index are reliable predictors of satiation or satiety compared to energy density and fiber content.   For example, boiled potatoes, which are relatively high in glycemic index, are also particularly satiating.  

The available evidence from intervention studies seems to support the idea that adding fruits and vegetables to meals can assist in weight control by adding water and fiber and reducing energy density, increasing satiation and satiety, and helping us to eat less overall while still getting good nutrition.  Supporting this idea, restricting high energy density foods while allowing unlimited amounts of fruits and vegetables has sometimes been a successful weight control strategy.  [3] 

This doesn't necessarily tell us that that adding fruits and vegetables to our diet causes us to eat less of other things, but it does tell us that we tend not to overeat fruits and vegetables, which suggests that many people find them either relatively satiating or relatively unpalatable.   So it leaves the door open to the possibility that they can be useful for weight control for those who do find them palatable as well as satiating. 

So let's assume for now that fruits and vegetables do help us with weight control by helping us eat less of other things.  That being the case does this still apply when the fruits and vegetables are prepared in a blender?

The answer to this might seem obvious depending on how you think about satiation and satiety.  The counter-intuitive reality though is that some foods increase in satiety when in liquid form and some foods decrease in satiety in liquid form.  The case is most clearly established for high sugar drinks, which have been unambiguously established to have very low satiation and satiety and are believed by obesity researchers to be an important  contributor to obesity.  The case is more equivocal for liquid meals that also contain more satiating ingredients such as fiber and protein.   In those cases, the variation in outcomes may be because the behavioral context plays a crucial role in their effect on intake. 

First, on the plus side, the water content of foods is one of the main things that increases how well they satisfy our appetite.  This happens by increasing their volume and their weight.  When you make a soup out of ingredients, you are getting both a greater weight and greater volume of food than when you eat the ingredients without the liquid, and in general that tends to increase the satiation of the same food without increasing the energy intake.  More interestingly, and more surprisingly, it can also increase the satiety of the same energy-equivalent of food, causing us eat less later.  [6]  For foods that are already satiating, adding water while still making them palatable and perceived as food, tends to increase satiation and satiety. 

The same effect is not seen simply by drinking water with a meal or before a meal as when the water is part of the food.  Hunger and thirst are regulated separately in the body, the satiating effect of fluids are because we  experience the food as heavier and higher volume (and as food!), not simply because there is more water in our stomach. 

Blending fruits and vegetables into a drink obviously increases the water content, and they are already satiating, so we have reason to suspect it might increase the satiety and satiation.  Assuming we experience it more as food rather than more as water.  So the case for losing weight with green smoothies seems plausible scientifically. 

On the minus side, we don't seem to regulate our own intake as well with a liquid diet as we do with a solid food diet. 

Under controlled conditions, where we are not inundated with abundance, variety, and other cues that tell us eat more, we tend to regulate our intake from one meal to the next during the day  to eat relatively the same amount from day to day, and we also seem to regulate out intake to some extent from day to day.    This is especially true of the volume of food we eat, but under some conditions it is also true of calories. 

Given the same weight and volume of solid food, we also tend to eat more or less from meal to meal to take in about the same amount of energy every day.    In experiments, secretly adding more calories to the same amount of food each day results in people eating less in subsequent meals.  This phenomenon of energy-specific satiety is sometimes known as dietary compensation.  [7],[8]    The argument against liquid diets is based on the finding that dietary compensation seems to be much weaker with liquid meals than with solid meals.  [9]  However this is mostly based on findings regarding fruit juices vs. fruit and sugary drinks vs. sugary solid foods, and almost entirely based on liquid vs. solid carbohydrate intake.  Liquid diets have also been used successfully for weight control under some conditions.  [10]

This means that different forms of a food (at least a carbohydrate) can alter its satiety and satiation, and the liquid form of carbohydrates in general seem to bypass our tendency to compensate by eating less.  With fruit for example, the case is quite clear, the liquid form is considerably less satisfying to our hunger when used as a "preload" just before eating.[11]    As usual, the energy density plays a big role, and fiber plays a smaller role, but simply drinking calories rather than eating them seems to have an independent effect on satiation as well.  This may be due to structural factors involved in eating and digestion or it may be due to expectations we have regarding how satisfying the food will be and the context in which we are eating. 

We probably don't expect fruit juice to satisfy our hunger as well as fruit, and that may in part be why it doesn't.  Do we expect smoothies to satisfy our hunger?  That might tell us whether they can serve us in weight control by helping us eat less in total. 

One strategy for eating less is sequencing.  Starting a meal with a low energy density food (as an appetizer or "pre-load") seems to reliably help us reach satiation with less total energy intake, but starting with solid low energy density food seems significantly more effective than starting with liquid low energy density food, regardless of fiber content.   This is in direct contrast to the popular advice to drink water prior to eating in order to fill up.  That seems relatively ineffective even if we replace the water a high fiber carbohydrate drink. 

Using a blender to conveniently add fruits and vegetables to our diet seems a reasonable strategy for weight control, by providing satisfying nutrition at lower energy intake, but the way we use it probably matters a lot.  It appears that blender meals are best used as weight control aids when: 

1. We enjoy them and find them palatable and satisfying  and expect them to be satisfying while still keeping them at low energy density. 
2. We do not make them energy-dense with sugars and fats, even "healthy" ones.
3. We use them to replace rather than just add more intake to higher energy density sources
4. They contain satiating ingredients such as high fiber carbohydrates and lean protein
5. We don't rely on them as our only strategy for getting good nutrition while taking in less energy

 References

[1](2004) Brownell, Kelly and Katherine Battle Horgen, "Food Fight: The Inside Story of the Food Industry, America's Obesity Crisis, & What We Can Do About It." McGraw-Hill

[2]  Michael G. Tordoff  (2002) "Obesity by choice: the powerful influence of nutrient availability on nutrient intake" 

American Journal of Physiology - Regulatory, Integrative and Comparative Physiology Published 1 May 2002 Vol. 282 no. 5, R1536-R1539 DOI: 10.1152/ajpregu.00739.2001  URL:  From http://ajpregu.physiology.org/content/282/5/R1536

[3] (2005) BARBARA J. ROLLS, PhD; ADAM DREWNOWSKI, PhD; JENNY H. LEDIKWE, PhD "Changing the Energy Density of the Diet as a Strategy for Weight Management"  Supplement to the Journal of the AMERICAN DIETETIC ASSOCIATION, May 2005 S98-S103

http://www.researchgate.net/profile/Jenny_Ledikwe/publication/7870238_Changing_the_Energy_Density_of_the_Diet_as_a_Strategy_for_Weight_Management/links/0f31752e8eb7a40544000000.pdf

 [4]  (2004) Barbara J. Rolls, Ph.D., Julia A. Ello-Martin, M.S., and Beth Carlton Tohill, Ph.D., M.S.P.H.  "What Can Intervention Studies Tell Us about the Relationship between Fruit and Vegetable Consumption and

Weight Management?"  Nutrition Reviews , Vol. 62, No. 1 January 2004: 1–17 URL: http://www.researchgate.net/profile/Barbara_Rolls/publication/8674390_What_can_intervention_studies_tell_us_about_the_relationship_between_fruit_and_vegetable_consumption_and_weight_management/links/5405d2cb0cf2c48563b1ba87.pdf

[5]  (2005) Tohill, Beth Carlton, "Dietary intake of fruit and vegetables and management of body weight," World Health Organization , ISBN 92 4 159284 2 URL: http://www.who.int/dietphysicalactivity/publications/en/f&v_weight_management.pdf

[6]   (1998) Barbara J Rolls, Victoria H Castellanos, Jason C Halford, Arun Kilara, Dinakar Panyam, Christine L Pelkman, Gerard P Smith, and Michelle L Thorwart    Am J Clin Nutr 1998;67:1170–77.

"Volume of food consumed affects satiety in men"  URL:  http://ajcn.nutrition.org/content/67/6/1170.full.pdf

[7]"Short Term Dietary Compensation in Free-Living Adults"

F. McKiernan, J.H. Hollis, and R.D. Mattes

Physiol Behav. 2008 March 18; 93(4-5): 975–983.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2323337/

[8] "Dietary compensation in response to covert imposition of negative energy

balance by removal of fat or carbohydrate"
Gail R. Goldberg*, Peter R. Murgatroyd, Aideen P. M. McKenna, Patricia M. Heavey
and Andrew M. Prentice
British Journal of Nutrition (1998), 80, 141–147
http://www.researchgate.net/profile/Peter_Murgatroyd/publication/13457513_Dietary_compensation_in_response_to_covert_imposition_of_negative_energy_balance_by_removal_of_fat_or_carbohydrate/links/0deec52cbd1ac48ea3000000.pdf

[9] (2000) "Liquid versus solid carbohydrate: effects on food intake and body weight"

International Journal of Obesity (2000) 24, 794±800
DP DiMeglio and RD Mattes
http://cibr.refrescantes.es/ka/apps/cibr/docs/06_2000_Solido_y_liquido_efecto_peso.pdf

[10] (2007) "Liquid calories, sugar, and body weight"

Adam Drewnowski and France Bellisle
Am J Clin Nutr March 2007 vol. 85 no. 3 651-661
URL: http://ajcn.nutrition.org/content/85/3/651.long

[11]  (2009) Julie E. Flood-Obbagy and Barbara J. Rolls "The effect of fruit in different forms on energy intake and satiety at a meal"   Appetite. 2009 April ; 52(2): 416–422. doi:10.1016/j.appet.2008.12.001.

URL:  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664987/?tool=pubmed

The argument for a SANE diet

This is the second in a series of commentaries on the ideas promoted in Jonathan Bailor's book "The Smarter Science of Slim."

This one presents my own spin on his argument for a SANE diet as an effective long term strategy for counteracting the trend toward obesity and obesity-related chronic illness.

In addition to recommendations for brief, infrequent, high intensity exercise to counter insulin resistance and reset metabolism, Bailor promotes what he calls a SANE diet. This is an acronym for satiety, "aggression", nutrition, and efficiency. Rather than duplicate his explanation, I'll just summarize by saying this refers to the quality of food rather than the quanitity, and takes a number of different quality factors into consideration. This note is intended to present my version of the argument for a mixed collection of quality factors in an anti-obesity strategy.

1. Human biology tends to regulate its body weight in a very narrow range for long periods under a wide range of natural and ancestral environments.

I came to understand this well over a decade ago and in my opinion the evidence base for it has grown rather than being seriously questioned in any significant way. This model does have a potentially misleading aspect to it in practice. Many people seem to assume that a body weight set point means different people are predisposed to different body weights. That is only partly true. The set point model does not assume a fixed value, it assumes that we tend to regulate our weight within a narrow range for long periods of time. It is obvious that the body fat set point changes over time, otherwise creeping obesity simply wouldn't happen. The issue is not whether the set point can change, but whether (and how) we change it in the other direction. The forces on it appear to be asymmetric.

My 1998 article on body fat regulation, showing the weak understanding I had at that point of the specifics but I think accurately depicting the concept and showing its historical origins and scientific rationale.

There have also been a number of helpful popular press articles expanding on the dynamic set point concept and its relation to weight loss plateau.

Obesity expert Arya Sharma discusses the set point concept and a unique theory of how it works.

2. Increasingly throughout the contemporary world, a combination of global economic drivers and local environments has created conditions that defeat the biology of weight regulation and cause body weight to creep upwards, resulting in an "obesity epidemic."

A recent Lancet special issue on obesity gave a summary of the current perspective on factors in obesity.


3. Clinical studies suggest a role for dietary glycaemic index (GI) in bodyweight regulation and diabetes risk.

There are a number of lines of evidence leading to the conclusion that glycemic index plays a central role in weight regulation through glucose homeostasis. I singled out this article because it also describes why some of the implications of that conclusion are controversial.

4. The effect of lowering GI is a dynamic change to metabolism, not a static linear dropping of weight because the body adapts to the loss of energy in order to maintain its set point. Static models of calories in vs. calories out do not take the effects of metabolism into consideration and therefore do not accurately predict weight loss.

Even though glycemic load is an important factor in obesity, we can't just cut out starches and sugars without making any other change and expect to keep losing weight. We will tend to compensate in other ways because of the significance of metabolism in weight regulation. As a result it is now considered essential to consider metabolism in predictions of weight loss rather than just calorie balance.

5. Solely manipulating GI in isolation has a diminishing return over time in weight loss because the reduction of calorie intake tends to slow metabolism and because of changes in potentially confounding dietary factors such as fiber content, protein content, palatability, and energy density.

This is a continuation of the previous claim, based on the evidence gathered from trying to control weight solely by reducing glycemic load.

6. CONCLUSION: An individual nutrition strategy that replaces high GI foods by taking energy density, palatability, fiber, protein, energy density, ad other factors into account can more successfully use a reduction in glycemic index to control body fat by improving fat metabolism, slowing or stopping the accumulation of insulin resistance, and reversing the upward creeping of the body fat set point..

None of that is particularly surprising scientifically as far as I know. The set point model of weight control has been standard in both human and animal research for a long time, it is not at all controversial among obesity and physiology researchers. You simply have to take metabolism into account when considering how the body absorbs, utilizes, and catabolizes nutrients and energy. You can't just assume that everything we take in minus some estimate of what we are "burning" is going to be an accurate model of body weight fluctuation.

The part where there is still room for argument is the specific causal sequence, and that has some additional implications. There's an old conundrum in psychology research: "do we cry because we are sad, or are we sad because we cry?" The answer seems intuitively obvious but it turns out that both causal models are partly right because there is a feedback look from our behavior to the way we feel.

There is a similar conundrum in obesity research. Do we get fat because we eat too much and don't move enough, or do we eat more and move less because of the effects of obesity. Again it turns out that both capture part of what is really going on. We do gain weight when we eat more and move less, at least in the short term before our metabolism starts to regulate our weight back to normal. But the thing that causes our weight to more permanently creep upward is the changes to our metabolism over time. And those hormonal and cellular changes make us less good at burning fat and better at absorbing it, changing our body fat set point over time.

Todd I. Stark
Nov 20,2011

Dietary fads, fictions, factions, and facts

This is my first post in a series of planned commentaries based on my reading of Jonathan Bailor's highly recommended book, "The Smarter Science of Slim."

This first commentary is my perspective on the history of the issues and how I perceive they have been resolved scientifically so far.

The Low Carb Revolution

Years ago, Dr. Atkins shocked popular culture and infuriated proponents of low fat diets with the claim that people could lose weight and reduce their risk of heart disease by minimizing the mainstay of the typical diet, carbohydrates, replacing them with proteins and fats.

This was a controversial claim not only because low fat diets were popular at the time but also because in emphasizing a low carbohydrate diet, Atkins was claiming that we could be healthy with minimal amounts of important dietary elements like fiber and the nutrition we get from vegetables. He was opposed by the people who promoted an ever higher proportion of vegetables in our diet and who encouraged us to minimize saturated fats, which were long widely thought to increase the risk of heart disease and obesity. At the same time, a lot of people argued that obesity can and should be sensibly addressed with the reasonable commonsense approach of eating a little less and moving a little more: get active and cut back a little on calories each day.

Two Battles Emerge

This turned into two polarized contests of opinion in popular culture.

First, there was a conflict between the folks who think quality of food is important in weight control and those who think that emphasis is misplaced, that we should just measure calories in and calories out. The implication of the food quality view: eating more of some things and less of others should affect our weight over time without making constant efforts to otherwise monitor and control our intake by counting calories. The implication of the calorie balance model: just eat a few calories less and move around a little bit more to burn a few more calories and you will lose weight consistently.

Second, among those who consider the quality of food to be important, there was the battle of the low-carb lobby vs. the vegetable lobby. Should you eliminate carbohydrates because of their effect on metabolism, or should you eliminate saturated fats because "fats make us fat" and raise blood cholesterol?

As is often the case in polarized positions it seems from our perspective today that both sides (in both contests) got some things right and both sides got some things wrong.

Calorie Balance vs. Metabolism: The Result

The standard and consensus view of obesity among researchers is that passive overeating is the best overall description of the cause. It is widely accepted, though not universally, that the amount of caloric energy we take in plays a causal role in obesity. Further the standard and consensus view is that this results from a combination of global economic factors and local environmental factors (the "obesogenic environment").

It is also a standard and consensus view among obesity researchers and physiologists that body weight is regulated by metabolic factors (via chemical messengers) that are not not related to the number of calories we take in and the number of calories estimated for the activity we perform.

What the calorie balance model captures: our biology doesn't violate the laws of conservation of mass and energy. Eating less and catabolizing body mass for energy does cause us to lose body mass. Eating more and demanding less energy utilization does cause us to gain body mass.

What the metabolism model captures: The calorie balance model clearly predicts that our body weight should consistently fluctuate according to the overall energy balance between what we take in and our activity. This is demonstrably not the case both from common experience and controlled studies. The prediction of the calorie balance model only apply for a short time and then our body changes internally to absorb food differently and to use it differently for energy. Our appetite and subjective energy levels are also changed. This is collectively expressed as the body regulating its mass in various ways around a relatively stable point.

The common experience of a "weight loss plateau" coincides with the concept of a "weight set point" around which our body maintains itself in a narrow range over time.

When we simply eat less, we lose weight for a little while and then the loss slows down and eventually stops and tends to reverse itself into return to baseline weight and sometimes even gain above that original level.

Further, the signficance of metabolism implies that quantity of energy taken in and demanded is only part of the causal model. Metabolism is affected differently by the specific foods we eat over time and the specific kinds of activities we engage in, not just or even primarily the total amount of energy involved. The metabolism model better captures the importance of food quality than does the calorie balance model.

Low Carb vs. Veggies: The Result

Given the consensus view that metabolism is an important factor in weight control and that the kinds of food we eat are an important factor in metabolism, we arrive at the second battle, over what it means to eat higher quality food more conducive to health and fighting obesity.

What the low carb lobby got right and the vegetable lobby got wrong: saturated fat isn't itself an important cause of heart disease and obesity. You can consume reasonable amounts of fat, including saturated fat from animal sources, and still have a very healthy diet.

What the low carb lobby got wrong and the vegetable lobby got right: The low carb lobby deals with the problems of insulin response in a gross and overly restrictive way by choosing proteins and fats over carbohydrates in general rather than balancing them and eliminating high glycemic carbohydrates. This makes levels of fiber too low and eliminates important sources of nutrients and often crowds out vegetable nutrition sources using animal ones. This is probably healthier than the typical high glycemic diet, but not nearly optimal. Minimizing carbohydrates is a bad strategy because we get many nutrients from carbohydrates, especially vegetables.

What both the low carb lobby and the vegetable lobby both got right from the start: Sugars and starches as a mainstay of our diet are killing many people. Insulin resistance is a precursor to type 2 diabetes and is associated with and exacerbated by a high glycemic diet as well as by obesity. Starches are high glycemic.

The low carb lobby recognizes the role of high glycemic foods in obesity and chronic illness but they generallize it too far to all carbohydrates as an overly restrictive and overly simplified strategy.

The vegetable lobby is too concerned with the role of animal fat in nutrition and focuses on that rather than the more important distinction of higher glycemic vs. lower glycemic carbohydrates and a more balanced diet.

Saturated fat doesn't itself cause heart disease or obesity. Combined with a high glycemic diet, saturated fat exacerbates the problems caused by constant massive triggering of the insulin response because of a combination of factors:

(1) fats plus sugars tend to increase appetite dramatically,

(2) fats have a high energy density compared to their nutrition,

(3) saturated fats in particular have no protective effect for heart disease compared to omega-3 from polyunsaturated fats.

People tend to lower their risk of heart disease when they switch from saturated to unsaturated fats. This is one of the strongest arguments for eliminating saturated fat from our diet. However it turns out that this benefit is probably not because saturated fats cause heart disease. It is more likely because unsaturated fats have a protective effect compared to saturated fats.

Lowering glycemic load allows us to use nutrients more effectively, to metabolize all fats more effectively, and tends to reduce the risk of heart disease and obesity far more than reducing saturated fats.

So what works?

What dietary strategy best lowers our risk of chronic illnesses and obesity? Do they all fail equally? Do different people respond differently to different regimens?

It turns out that individuality is a real factor, both biochemical and psychological, and learning to make the principles work in your own life and for your own biology is critical. Still, there are also some general principles that we can rely on as a very good start.

The low carb strategy often works for as long as people can manage to maintain it and is healthier than the typical diet but it is not optimal for health and most people find it hard to sustain and eventually have health problems or fail to sustain it. It is not balanced nutritionally, it is too severe in limiting valuable and healthy vegetable sources of nutrition.

A vegetarian strategy often works at least for a while and is also healthier than the typical diet but it is also difficult for most people to maintain and as a general strategy it is too severe in limiting valuable and healthy animal sources of protein and what for many people are satisfying sources of texture and flavor in animal fats.

Taking what they both get right and eliminating what each gets wrong, we end up with:

1. Avoid high glycemic carbohydrates as far as possible or only under very specific conditions.

As a mainstay of our diet are a primary cause of both obesity and chronic illnesses via their effect on our response to insulin and our ability to absorb and metabolize nutrients. In other words, these commonly accepted processed products of agriculture cause a "clogging" of our metabolism over time that defeats our evolved ability to regulate our own metabolism. High glycemic carbohydrates are not essential for health and we tend to become dependent on them in various ways so minimizing them is an important first step to better health. There are specific strategies you can use to minimize their negative effects if you want to use them for athletic reasons or because you can't bear to eliminate them from your life entirely, but you have to be wary of how often you do this and the timing of it.

2. Balance the remaining nutrients between proteins, low-glycemic carbohydrates, and fats.

Compared to high glycemic foods, these categories all contain many healthy and valuable sources of nutrition.

Why a balance? In addition to just having a variety of nutrients of different kinds as well as a variety of tastes and textures to make eating more satisfying, there are also some specific nutritional reasons.

A diet of too much fat and too little protein and carbohydrate fails because fat contains relatively little nutrition compared to its energy density and tends to crowd out our intake of fiber important to digestive health as well as various nutrients. A diet of too much fat also fails because we have to eat a lot of it to make us feel satisfied in lieu of protein, fiber and water because of its low nutritional density.

A diet of too much protein fails because it avoids fiber and avoids important sources of vitamins and minerals and because it requires us to limit our protein sources very severely. It is also unhealthy to take in extreme amounts of protein. You can live on a high protein diet for a while if it isn't too high, but it isn't optimal. Temporary protein-sparing fasts are effective and popular among some athletes.

A diet of too much low-glycemic carbohydrates (taken to an extreme this would basically be a vegetarian diet that not only minimizes starches and sugars, but also seeds, nuts, and soy) is not really something anyone seriously recommends or practices as far as I know, but if they did it would fail because it would not have adequate protein sources to sustain health and would be relatively unsatisfying. Even strict vegans eat vegetable protein and fat sources, they just avoid animal sources. A diet with a huge amount of low-glycemic carbohydrates is perfectly healthy and sustainable so long as it also includes a reasonable amount of plant fat and protein sources.

The lesson here is just to mostly eat natural foods while avoiding high glycemic carbohydrates rather than striving for extremes of individual components. Avoid high glycemic foods and otherwise eat to satisfy your hunger. The specifics of satisfying our hunger are important however, balance is important in order to get a good combination of fiber, protein, water, nutrition, taste, texture, and other factors to satisfy us.

3. Take advantage of the "Paleo" principle but don't be limited entirely by it

I think the principle behind "Paleo" diets is basically correct, that our metabolism seems to be tuned by evolution to process natural animal and plant sources of nutriton that we could hunt or gather, and has not adapted yet to our dietary preponderance of processed agricultural products. This is another way of saying that high glycemic carbohydrates (the main category of highly processed and cultivated foods in our diet: the wheat, corn, potato, and rice products) are a very bad thing to emphasize all of the time.

In general the principles behind paleo eating agree with those proposed here, however they also focus on a rationale that can be misleading, which is why I consider it a fad even though it gets things mostly right. Trying to guess what our ancestors might have eaten and in what amounts is not nearly as useful a way to figure out what is healthy as just applying general principles and nutritional research results. By all means it makes sense to look to Paleo recipes and products as candidates for making it easier to maintain good nutrition. Also it is convenient and useful to imagine whether something could be hunted or gathered to know whether it is a nutritional source likely to be compatible with our metabolism.

Just don't limit yourself to the principle that we can only eat what our ancestors ate or elaborate arguments about the Pleistocene lifestyle. You have more options which you can intelligently apply to use modern foods and still be healthy.

4. Don't expect restricting calories to help you in the long run if you are eating poorly.

If you stop eating competely, you eventually die because your body eats its own tissue to try to meet its energy requirements. So when we talk about calorie restriction we aren't talking about not eating. We are talking about changing the timing of when we eat and eating less in a given period relative to what we would normally eat. We might eat less in a given period than we otherwise would, or we might eat nothing for a specific period of time. There are many strategies for calorie restriction. Some of them have a place in athletic performance and some of them can also have a place in a health regimen, but we have to be careful about how we go about it and how much we rely on it.

Sometimes the most reasonable approach is not the best. Portion control and light or moderate exercise seem perfectly reasonable and have been long recommended as a treatment or prevention for obesity. But for the vast majority of people they don't work for this purpose. Our metabolism and appetite conspire to maintain a stable weight against our efforts to make small reasonable changes in how much we eat and how much we move. We have to more directly influence our appetite and metabolism to deal with obesity. Simply eating less of the same things we are eating does not neccessarily help because it does not address the metabolic causes of our problems.

Fasting, as opposed to portion control, is a more potentially valuable and effective health strategy. This is because it can help you learn how to better control cravings, and can help you get your body fat lower than you could reasonably get with frequent eating and for longer periods. Some evidence suggests that fasting itself might trigger healthy changes in the body, although these are hard to distinguish from just the benefits of controlling body fat and eating more healthy overall. Fasting is much more difficult to do effectively, much less sustainable, and much less effective and healthy when combined with a high glycemic diet.

Your best bet is probably to eliminate high glycemic carbohydrates and get the hang of eating well first, then try fasting as an additional strategy if you want to, to make it even more effective and sustainable.

5. Don't just load up on "low fat" foods. But do emphasize lean protein sources over fatty ones.

By the best evidence available now, it seems that reducing fat by itself plays virtually no role in controlling obesity or chronic illness. Nutritionally, fat should be considered "neutral" or "filler" compared to good nutritional sources like non-starchy vegetables and good protein sources like seafood, lean meats, and egg whites. The problem with a "low fat" strategy is that if you go out of your way to avoid fats, you will also tend to replace the missing energy with starches and sugars.

If you could eliminate fats without replacing them with high glycemic foods, this strategy would probably work a lot better. Lean protein sources are an important part of modern nutrition, not because fat is bad, but because protein is so valuable. Fatty protein sources are really fats, not proteins, so they should be considered filler in your diet, rather than assuming they are good sources of protein. You have to eat an unreasonable amount of fatty protein sources to get enough protein to be valuable for satiety and nutrition.

6. If you find yourself eating something high-glycemic, at least mitigate its effects with fiber and protein and avoid fat under those conditions.

The effect of food on our insulin levels is the primarily culprit in obesity and many chronic diseases. However this glycemic effect is not just a result of what individual foods we eat, it is result of their combined effect on the amount of glucose circulating in our blood. There is no way to simply counter-act the glycemic effect short of avoiding high glycemic foods entirely but you can reduce it by lowering the combined glycemic effect by increasing the amount of fiber and protein you eat along with high glycemic foods. If you are going to indulge in high glycemic food, you can reduce the damage it causes by avoid simultaneous eating of fats (which boost appetite strikingly when combined with starches and sugars) and eat lean protein and good fiber sources with the high glycemic foods instead.

Note: This article was inspired by Jonathan Bailor's highly recommended book, "The Smarter Science of Slim."

Todd I. Stark
Nov 20,2011